The evolution of the structural, electrical and magnetic properties with the isovalent chemical substitution of Ca 2 + into the Sr 2 + sites in the new series of two-dimensional La 1 . 2 (Sr 1 . 8 - x Ca x )Mn 2 O 7 samples (0=<x=<0.8) and three-dimensional La 0 . 6 (Sr 0 . 4 - x Ca x )MnO 3 samples (0=<x=<0.4) has been investigated. The compositional dependence of the structural variation has been found in La 0 . 6 (Sr 0 . 4 - x Ca x )MnO 3 . The Curie temperatures (T C ) decreased from 135 to 102K and 370 to 270K for x=0-0.4 in La 1 . 2 (Sr 1 . 8 - x Ca x )Mn 2 O 7 and La 0 . 6 (Sr 0 . 4 - x Ca x )MnO 3 , respectively. Our results confirm that the dimensionality as well as ionic size plays an important role in controlling the colossal magnetoresistance in manganites.